Wireless communication networks are well known. Some networks are completely proprietary, while others are subject to one or more standards to allow various vendors to manufacture equipment, such as wireless terminals, for a common system. One such standards-based network is the Universal Mobile Telecommunications System (UMTS). UMTS is standardized by the Third Generation Partnership Project (3GPP), collaboration between groups of telecommunications associations to make a globally applicable third generation (3G) mobile phone system specification within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). Efforts are currently underway to develop an evolved UMTS standard, which is typically referred to as UMTS Long Term Evolution (LTE) or Evolved UMTS Terrestrial Radio Access (E-UTRA).
According to Release 8 of the E-UTRA or LTE standard or specification, downlink communications from a base station (also known as an “enhanced Node-B” or simply “eNB”) to a wireless terminal, or communication device, (also known as “user equipment” or “UE”) utilize orthogonal frequency division multiplexing (OFDM). In OFDM, orthogonal subcarriers are modulated with a digital stream, which may include data, control information, or other information, so as to form a set of OFDM symbols. The subcarriers may be contiguous or non-contiguous, and the downlink data modulation may be performed using quadrature phase shift-keying (QPSK), 16-ary quadrature amplitude modulation (16QAM), 64-ary quadrature amplitude modulation (64QAM), or the like. The OFDM symbols are configured into a downlink sub frame for transmission from the base station. Each OFDM symbol has a time duration and is associated with a cyclic prefix (CP). A cyclic prefix is essentially a guard period between successive OFDM symbols in a sub frame. According to the E-UTRA specification, a normal cyclic prefix is about five (5) microseconds and an extended cyclic prefix is about 16.67 microseconds.
In contrast to the downlink, uplink communications from the UE to the eNB utilize single-carrier frequency division multiple access (SC-FDMA) according to the E-UTRA standard. In SC-FDMA, block transmission of QAM data symbols is performed by first discrete Fourier transform (DFT)-spreading (or precoding) followed by subcarrier mapping to a conventional OFDM modulator. The use of DFT precoding allows a moderate cubic metric/peak-to-average power ratio (PAPR) leading to reduced cost, size and power consumption of the UE power amplifier. In accordance with SC-FDMA, each subcarrier used for uplink transmission includes information for all the transmitted modulated signals, with the input data stream being spread over them. The data transmission in the uplink is controlled by the eNB, involving transmission of scheduling requests (and scheduling information) sent via downlink control channels. Scheduling grants for uplink transmissions are provided by the eNB on the downlink and include, among other things, a resource allocation (e.g., a resource block size per one millisecond (ms) interval) and an identification of the modulation to be used for the uplink transmissions. With the addition of higher order modulation and adaptive modulation and coding (AMC), large spectral efficiency is possible by scheduling users with favorable channel conditions.
E-UTRA systems also facilitate the use of multiple input and multiple output (MIMO) antenna systems on the downlink to increase capacity. As is known, and illustrated in FIG. 2, MIMO antenna systems are employed at the eNB 202 through use of multiple transmit antennas 204 and at the UE through use of multiple receive antennas. A UE may rely on a pilot or reference symbol (RS) sent from the eNB 202 for channel estimation, subsequent data demodulation, and link quality measurement for reporting. The link quality measurements for feedback may include such spatial parameters as rank indicator, or the number of data streams sent on the same resources; precoding matrix index (PMI); and coding parameters, such as a modulation and coding scheme (MCS) or a channel quality indicator (CQI). For example, if a UE determines that the link can support a rank greater than one, it may report multiple CQI values (e.g., two CQI values when rank=2). Further, the link quality measurements may be reported on a periodic or aperiodic basis, as instructed by an eNB, in one of the supported feedback modes. The reports may include wideband or subband frequency selective information of the parameters. The eNB may use the rank information, the CQI, and other parameters, such as uplink quality information, to serve the UE on the uplink and downlink channels.
As is also known, present-day cellular telephones include global positioning system (GPS) receivers to assist in locating the devices and their owners in the event of an emergency and to comply with E-911 mandates from the Federal Communication Commission (FCC). Under most circumstances, the phone's GPS receiver can receive signals from the appropriate quantity of GPS satellites and convey that information to the cellular system's infrastructure for determination of the device's location by, for example, a location server coupled to or forming part of the wireless network. However, there are some circumstances under which the GPS receiver is ineffective. For example, when a user and his or her cell phone are located within a building, the GPS receiver may not be able to receive signals from an appropriate quantity of GPS satellites to enable the location server to determine the device's position. Additionally, wireless devices in private systems are not required to meet the FCC E-911 mandates and may not include a GPS receiver. However, circumstances may arise under which determining locations of wireless devices operating in such systems may be necessary.
To compensate for possible intermittent ineffectiveness of the GPS system and to provide location-determining capabilities in private systems, many wireless systems utilize signaling and include processes through which a wireless device's location can be estimated. For example, in many systems, base stations regularly transmit positioning reference signals that are received by the wireless devices and used either to determine information based upon which an infrastructure device, such as a location server, can compute (e.g., via triangulation and/or trilateration) the wireless device's location or to determine the location of the wireless device autonomously (i.e., at the wireless device itself). When a location server is intended to compute the wireless device's location, the wireless device may determine time of arrival (TOA) or time difference of arrival (TDOA) information upon receiving the positioning reference signal and communicate the TOA or TDOA to the location server via a serving base station (i.e., a base station providing wireless communication service to the wireless device). The TOA or TDOA information is typically determined based on an internal clock of the wireless device as established by the wireless device's local oscillator in accordance with known techniques.
Work is in progress in the 3GPP wireless standards forum to provide means for positioning mechanisms that achieve parity with or even surpass the capabilities and performance currently provided for other wireless access types including GSM, WCDMA, 1×RTT and EV-DO. It is an objective of this work to include support for positioning capabilities and features in association with LTE access while ensuring backward compatibility with networks and UEs that support LTE and EPS according to Rel-8 of the 3GPP standards. The desired positioning capabilities and features include:                a positioning protocol or protocols compatible with and enabling support for both the control plane LCS solution for EPS and OMA SUPL;        UE assisted and UE based assisted Global navigation satellite system (A-GNSS);        a downlink terrestrial positioning method, analogous to E-OTD, OTDOA and AFLT, capable of operating in UE assisted and UE based modes (note that a single downlink method will be defined); and        enhanced cell ID measurements coming from the UE and/or eNode B.        
Possible extensions of existing mobility measurement reporting in LTE Rel-8 are proposed in support of a downlink method—such as an Observed Time Difference of Arrival or OTDOA or, shortened, OTD method. Methods are known that are UE-centric (where the UE can generate a positional fix without the delivery by the network of ancillary data) and other methods are UE-assisted (where the UE's measurements are delivered to the network or a network component such as a Location Server (LS), for combination with other data to generate a location fix).
It is possible to report a combination of target cell physical cell identity (PCID) and reference signal received power (RSRP) with the addition of UE-measured cell relative timing information to form a measurement “triplet”—i.e. PCID, RSRP, and relative cell timing with respect to some reference cell for example, the serving cell, where in the serving cell could consist of one or more non-colocated cells. Similar approaches are known to be supported in WiMAX or generic CDMA systems, including WCDMA.
The application of such techniques are known even if the network is not synchronous, including the case where the base stations comprising the network are not aligned in time but have a known mutual timing offset.
Specifically, the UE reports relative timing for both synchronous and asynchronous cells, and it is then up to the network to make any corrections for relative inter-BS (base station) timing to permit location fixing to be accomplished.
The network, or LS, can further transmit relative eNB timing to allow the UE to perform autonomous fixes (UE-centric), but this also requires the network or LS to make available to the UE, or a secure entity in the UE, specific eNB locations, which the network operator may not wish to do.